Many foods have relatively short shelf lives due to the presence of undesired contaminants such as yeasts and moulds. Such yeasts and moulds cause undesired spoilage, and often render the foods inedible.
It is known to inactivate undesirable microorganisms in food by a variety of methods, the most common of which is heating. Heat treatment can significantly improve both the safety and the keeping quality of the food. In particular the shelf life of the food can be extended.
However, properties such as the taste, texture, and nutritional quality of some foods can be compromised by a heat treatment. For example, heat-treated meat can have unacceptable cooked flavour. A heat-treated cultured milk product such as yoghurt does not contain a live bacterial culture, as the culture is inactivated by the treatment.
It was recognised at the beginning of the last century, that bacteria used for the fermentation of products such as yoghurt, are of benefit to human health if consumed alive. It is now recognised that certain cultures of live micro-organisms, defined as probiotic, exert health benefits beyond basic nutrition upon ingestion in certain numbers. (Holzapfel et al). It is known to add these probiotic bacteria to foods (Lee and Salaminen) for delivery by ingestion. However, it is difficult to deliver such bacteria in sufficient numbers in a food that is subsequently heat-treated.
It is an object of the present invention to provide an improved or alternative method of treating a food product, and/or to go at least some way to overcoming the problems encountered with the prior art.